pxt-microbit Accessibility PR (#529)

* Accessibility changes

docs/projects/hack-your-headphones/code.md

@@ -1,10 +1,10 @@
 # Code
 
-### ~avatar avatar
+## ~avatar avatar
 
 Have you ever tried to making beat box sounds based on the light level? Let's try making a beatbox with code!
 
-### ~
+## ~
 
 Let's start by adding a variable where you can store data. Then rename the variable to "light". Then set the value of the variable to the block `light level` from the Input drawer. This will gets the `light level` from 0 (dark) to 255 (bright). The light is measured by using various LEDs from the screen. Modify your code so that your code looks like this.
 

docs/projects/hack-your-headphones/make.md

@@ -1,24 +1,24 @@
 # Make
 
-### ~avatar avatar
+## ~avatar avatar
 
 Did you know you could attach your headhpones to the @boardname@ to generate sounds?
 
-### ~
+## ~
 
 # ~hint
 
-**No crocodile clips!?!?!** Use wires or Aluminium foil! [Read more...](/device/foil-circuits)
+**No crocodile clips!?!?!** Use [wires or aluminium foil](/device/foil-circuits)!
 
 # ~
 
-### Step 1
+## Step 1
 
 ![](/static/mb/lessons/banana-keyboard-1.png)
 
 Using the 1st crocodile clip, connect the end of the crocodile clip onto GND pin on the @boardname@.
 
-### Step 2
+## Step 2
 
 ![](/static/mb/lessons/banana-keyboard-2.png)
 
@@ -26,13 +26,13 @@ Using the 1st crocodile clip, connect the end of the crocodile clip onto GND pin
 
 Using the 2nd crocodile clip, connect the end of the crocodile clip onto the 0 pin on the @boardname@.
 
-### Step 3
+## Step 3
 
 ![](/static/mb/lessons/banana-keyboard-4.png)
 
 Using the 1st crocodile clip, connect the second end of the crocodile clip onto based of the headphone jack. The base of your headphone jack is considered the ground so it is connected to the GND of the @boardname@.
 
-### Step 4
+## Step 4
 
 ![](/static/mb/lessons/banana-keyboard-5.png)
 
@@ -40,14 +40,14 @@ Using the 1st crocodile clip, connect the second end of the crocodile clip onto
 
 Using the 2nd crocodile clip, connect the second end of the crocodile clip onto the tip of the headphone jack. The tip of your headphone jack feeds into the right speaker on the headphone. You connect from the @boardname@ pin 0 to the tip of the right side of your headphone. Use the tip of the headphone jack to play sounds.
 
-### Step 5
+## Step 5
 
 ![](/static/mb/lessons/hack-your-headphones-0.png)
 
 You hacked your headphones!
 
-### ~button /projects/hack-your-headphones/code
+## ~button /projects/hack-your-headphones/code
 
 NEXT: music of light
 
-### ~
+## ~